Synchronization indicator for internal combustion engines



April 4, 1939. c. l. McNElL 2,153,264

SYNCHRONIZATION INDICATOR FOR INTERNAL COMBUSTION ENGINES Filed Oct. 1,1935 ENG/NE A l ENG/NE -B 24 v g 36 33 2a 2 a4 67 a 3 6 DCPOWER L/ E Kmar/Em INVENTOR- Char/es f. Mc/l/ef/ PatentedApr. 4, 1939 UNITED STATESPATENT OFFICE SYNCHRONIZATION INDICATOR FOR IN- TERNAL COMBUSTIONENGINES Application October 1, 1935, Serial No. 43,105

2 Claims. 1C1. 177- 311) This invention relates to internal combustionengines and particularly to a plurality of such engines having atendency to deviate from a desired common speed.

5 An object of the invention is to provide an indicating systemincluding a synchroscope and means for causing said synchrosc'ope toassume a definite position or condition when the subjects of study, suchas the internal combustion engines above suggested, are operating insynchronism, and to display a difierent type of indication when saidengines are rotating at different speeds.

Another object is to provide, in a system of the indicated character, amotion differential device and novel operating means therefor, includingsynchronous alterating current motors, and means for translating therotation of the respective subject engines into alternating currentimpulses of a magnitude and frequency which corresponds in each instanceto the speed of the associated engine.

These and other objects of the invention will become apparent frominspection of the following specification when read with reference tothe accompanying drawing wherein is illustrated the preferred embodimentof the invention. It is to be expressly understood, however, that thedrawing is for the purpose of illustration only, and is not designed asa definition of the limits of the invention, reference being had to theappended claims for this purpose.

In the drawing: Fig. l is a schematic representation of one embodimentof the invention; and Fig. 2 is a schematic representation of a secondembodiment.

Referring first to Fig. 1, reference characters ii and 1 indicate theelectrical features of a pair of magnetos, each having a rotor driven inthe usual mechanical way (not shown) from the crankshaft of theassociated engine whose speed, in relation to that of the second engine,is to be indicated. The electrical circuits of the magnetos include theusual primary and secondary windings l5 8 and 9, l land i2 respectively,and the usual condensers it and M, and periodically opened circuitbreakers l6 and W, one side of the circuits bein grounded, as indicatedat It and IS. The usual wires for grounding the magneto circuits arerepresented at 2| and 22, connecting to switches 23 andt24, locatedwithin reach of the chauffeur or pilo In order to produce, from thevoltage impulses generated by the magnetos, alternating current tooperate the synchronous motors 26 and 21, at

voltages corresponding to the frequency of the said magneto voltageimpulses, I connect said motors 26 and 21 in the plate circuits of theoscillating current generators 28 and 29. These oscillating currentgenerators 28 and 29 are shown 5 as conventional vacuum tubes havingtheir two major electrodes connected to the positive and negativeterminals of a suitable D. C. power supply 3l and 32, and their gridelectrodes connected to magneto control circuits 2| and 22, through 10leads 33 and 34, containing resistors 36 and 31,

of high resistance of the order of five to ten thousand ohms for eachmillimeter of spark gap in the secondary circuits of the magnetos.

With this arrangement, the current in the circuit to each synchronousmotor will oscillate at a rate determined by the frequency of thevoltage impulses generated by the magneto and will cause the platecircuit of the associated power amplifier 28 or 29, to' generate analternating current 2 at a voltage which will correspond to suchfrequency, and thereby maintain the speed of the associated motor 26 and21, in synchronism with the magneto speed; and by mechanicallyconnectlng the rotors of the motors 26 and 21 through differentialgearing 38 the movement, or lack of movement, of the pointer (notrshown,and connected to the resultant gear shaft) will indicate the degree ofasynchronism, if any, between the speeds of the two subject engines. 30

It should be noted that an outstanding advantage cf the method of speedtranslation above described, is the simplicity of the electricalinstallation work; the only added equipment, over and above that whichis standard on all modem 35 transport planes and military aircraft,being the motors 26 and 21, and the wire to the oscillator.

It will also be noted that there are no mechanical attachments to theengine, and no additional wiring between the engine compartment and the40 cabin of the plane.

In the embodiment of Fig. 2 the motors 2B and 21 receive their energyfrom the secondaries of two transformers 4|, 42, whose primary currentsoriginate from a power source 39 and are sub- 4 ject to interruption bythe rotation of cams 43 and 44 operating on normally closed contacts 46and 41 respectively, the cams being-rotatable mechanically throughsuitable connections (not shown) to the respective engines whose speedsare 50 to be indicated. These interrupters of the primary circuits willcause pulsating current and these pulsations will be reflected in theresulting voltage values in the secondary circuits which energize themotors 26 and 21. The said motors 55 will accordingly acquire speedssynchronizing with those of the subject engines, and the degree ofasynchronism, if any, will be indicated by the pointer, as aboveexplained in describing Fig. 1.

currents, and diflerential means connecting said motors whereby anindication of the diiierence in frequency of interruption and hence ofthe speed 0! said engines is given.

2. In a system for indicating synchronism 01' a pair of internalcombustion engines, the combination with a pair of freely rotatablesynchronous alternating current motors of means for synchronizing one orsaid motors with one or said engines, means for synchronizing the otherof said motors with the other of said engines, said two synchronizingmeans including ignition circuit breaker points actuated by therespective engines, secondary circuits linked to the respective ignitioncircuits, means for causing the current flow in the respective secondarycircuits to pulsate with each opening of the corresponding breakerpoints, means to transform the respective pulsating currents intocurrents operative to energize i said synchronous motors, anddifferential means coupling said motors whereby an indication of thediiference in frequency of interruption and hence oi the speed of saidengines is given.

CHARLES I. MCNEIL.

